The present specification generally relates to throughput determination procedures in network deployments. For example implementing carrier aggregation (CA) aggregating a primary cell and at least one secondary cell.
LTE-Advanced (LTE-A) aims to support peak data rates of 1 Gbps in the downlink and 500 Mbps in the uplink. In order to fulfill such requirements, a transmission bandwidth of up to 100 MHz is required. Since the availability of such large portions of contiguous spectrum is rare in practice, LTE-A utilizes carrier aggregation of multiple component carriers (CC) to achieve high bandwidth transmission. In doing so, LTE-A supports aggregation of up to five 20 MHz CCs.
All CCs in Long Term Evolution (LTE) Release 10 are designed to be backward-compatible. This means, that it is possible to configure each CC such that it is fully accessible to LTE Release 8 User Equipments (UE). From the higher-layer perspective, each CC appears as a separate cell with its own Cell identifier (ID). A UE that is configured for carrier aggregation connects to a Primary Serving Cell, which is known as PCell and up to four Secondary Serving Cells, which are known as SCell. The PCell is defined as the cell that is initially configured during connection establishment. The PCell plays a role with respect to security, non-access stratum (NAS) mobility information, system information (SI) for configured cells, and some lower layer functions.
After the initial security activation procedure, Evolved Universal Terrestrial Radio Access Network (E-UTRAN) may configure a UE, which supports carrier aggregation, with one or more SCells in addition to the PCell which is initially configured during connection establishment. The configured set of serving cells for a UE always contains one PCell and may also contain one or more SCells. The number of serving cells that can be configured may depend on the aggregation capability of a UE. A single Radio Resource Control (RRC) connection is established with the PCell, which may control all the CCs configured for a UE.
After RRC connection establishment to the PCell is performed, reconfiguration, addition and removal of SCells may be performed by RRC. In connected mode, changes of SI for a SCell are handled by release and addition of the affected SCell. Such release and addition may be done with a single RRC reconfiguration message.
In addition to discontinuous reception (DRX) operations, some kind of UE power saving may be achieved by fast activation and deactivation of individual SCells. Of course, the PCell may not be deactivated. When a SCell is deactivated, the UE may not have to receive data transmissions or monitor a physical downlink control channel (PDCCH) for that SCell, thus saving power. Activation and deactivation of SCells may be under evolved Node B (eNodeB, eNB) control. The activation and deactivation may be executed by means of medium access control (MAC) control elements, which can activate or deactivate one or more SCells indicated by an 8-bitmap. A timer may also be used for automatic deactivation if no data or PDCCH messages are received on a CC for a certain period.
The timing of activation and deactivation may be defined in order to ensure that there is a common understanding between the eNB and the UE. If a MAC control element activating a SCell is received in subframe n, then the SCell has to be ready for operation for example no later than in subframe n+8. If a MAC control element deactivating a SCell is received, or a deactivation timer expires, in subframe n, channel state information (CSI) report may cease from subframe n+8 on.
3rd Generation Partnership Project (3GPP) radio access network (RAN) and service and system aspects (SA) specifications widely standardize different aspects of CA functionality. An ongoing LTE Release 11 SA work item (WI) on management of CA for LTE reveals that CA influences performance measurements and there may be a need to extend existing methods.
Further, with respect to RAN measurement definitions for scheduled internet protocol (IP) throughput are developed in order to address various requirements on reflecting quality of service (QoS) in new and upcoming network deployments. The measurement is expected to be further examined, in particular under LTE Release 12 WI on further enhancements for minimization of drive tests (MDT). The WI objective aims at QoS related enhancements, and is treated also in context of CA.
Discussions of 3GPP under LTE Release 11 SA5 WI management of CA for LTE, which relates to how to monitor data rates that are visible both from cell and also end user point of view on packet data configuration protocol (PDCP) layer, are ongoing but no clear solution is available/agreed yet.
As mentioned above, from the perspective of a NAS, a UE is connected to a respective PCell. Other CCs are simply considered as additional transmission resources.
The multiple CCs of carrier aggregation may be not visible to PDCP and radio link control (RLC) layers. The respective protocols may therefore remain unchanged from LTE Release 8 except possible amendments to enable supporting data rate up to 1 Gbps.
One main benefit of CA feature as already mentioned is held to be supporting higher data rates. These, of course, shall be visible both from cell and also end user point of view on PDCP layer. The operator therefore should have reliable indicators/measurements to monitor and evaluate the same. Accordingly, evaluation of CA performance is an interested topic in 3GPP. However solutions therefore are missing by now.
FIG. 8 is an exemplary block diagram illustrating an overview of the user plane architecture in downlink direction. It is derivable from the overview given in FIG. 8 that multiple CCs of carrier aggregation are visible from MAC layer, namely, each CC may have its own independent hybrid automatic repeat request (HARQ) entity in MAC layer. However, as mentioned above, the multiple CCs of carrier aggregation may not be visible to the PDCP and RLC layers.
In general, PDCP service data unit (SDU) cell throughput and total IP scheduled (end user) throughput may be measured with techniques known from previous releases according to 3GPP. However, problems rise when IP scheduled (end user) throughput for CA UEs with part of data transmitted via SCell is to be evaluated. As the CA feature is intended to be applied only on restricted number of UEs, it is important to measure the IP scheduled throughput of those group of UEs only in order to be able to demonstrate the benefit of the feature. In this regard it is noted that providing a total end user throughput may deform and underestimate the benefits of the CA feature.
Main reasons for above mentioned problems are that the multiple CCs of carrier aggregation may be visible neither to the PDCP nor to RLC layer, and that one PDCP SDU frame related to CA UE with activated one or more SCells may be e.g. partly transmitted via PCell and one of the SCells, or via two SCells configured for the UE. In generic terms, neither from PDCP nor RLC layers view it can not be determined whether and how many SCells are involved in a considered transmission, such that it is not possible to form a CA related scheduled IP throughput conclusion.
In current LTE Release 11 RAN MDT WIs finer granularity in determination of scheduled IP throughput is introduced. However, since the reference points for measurement are not changed, the above mentioned problems are not overcome, i.e. e.g. the benefit of data transmitted over SCells is still not possible/visible to measure.
Hence, there is a need to provide for evaluation of throughput of carrier aggregated user equipments.